Which is more cost-effective, GPT-5.6 Terra or Gemini 3.1 Pro?

Based on 1M input + 1M output tokens, GPT-5.6 Terra costs $14.00/month versus Gemini 3.1 Pro at $14.00/month. The cheaper option depends on your token volume and prompt-to-completion ratio. Use the interactive calculator on this page to enter your exact usage.

How accurate is this cost comparison?

List prices come from each provider's own pricing page and every model page shows when they were last verified. The capability scores are iOPTERA's editorial composites — informed by public benchmarks, not benchmark results themselves; the methodology page explains how they are set.

Which model scores higher on benchmarks?

GPT-5.6 Terra scores 93 in coding and 94 in reasoning benchmarks. Gemini 3.1 Pro scores 88 in coding and 89 in reasoning. See the full 5-category breakdown in the Benchmark Comparison section above.

What are the context window sizes of GPT-5.6 Terra and Gemini 3.1 Pro?

GPT-5.6 Terra supports a 1.1M-token context window while Gemini 3.1 Pro supports 1.0M tokens. A larger context window lets you process more text in a single API call.

Which model is faster for real-time applications?

GPT-5.6 Terra has a speed score of 86/100 and Gemini 3.1 Pro scores 82/100 on our latency benchmark. For interactive chatbots and low-latency tasks, the higher speed score is preferable.

Can I calculate costs for my specific token volume?

Yes. Use the interactive cost calculator on this page. Enter your monthly token volume and adjust the prompt-to-completion ratio. You can also use presets for common scenarios like Customer Support Bots (~30M tokens/month) or Document Summarizers (~15M tokens/month).

Cost and performance comparison

GPT-5.6 Terra vs Gemini 3.1 Pro

Model AOpenAI

GPT-5.6 Terra

Capability score (editorial)94/100

Cost / 1M Tokens: $5.00; 70% in · 30% out mix
Value Index (score÷cost): 18.8; Higher = better value

Speed: 86/100
Context: 1.1M
Tier: Smart Tier

List price from the OpenAI pricing page, verified October 12, 2026.

Check the source

How we verify prices

Model BGoogle

Gemini 3.1 Pro

Capability score (editorial)89/100

Cost / 1M Tokens: $5.00; 70% in · 30% out mix
Value Index (score÷cost): 18.4; Higher = better value

Speed: 82/100
Context: 1.0M
Tier: Smart Tier

List price from the Google pricing page, verified October 12, 2026.

Check the source

How we verify prices

In-depth analysis

GPT-5.6 Terra vs Gemini 3.1 Pro: Detailed Comparison

GPT-5.6 Terra is OpenAI's mid-range-tier language model with a 1.1M-token context window, excelling at reasoning. Gemini 3.1 Pro from Google is a mid-range-tier model supporting 1.0M tokens in context, with standout performance in vision/multimodal.

Price is not the deciding factor here. For the same text, Gemini 3.1 Pro and GPT-5.6 Terra land within 3% of each other, which is inside the margin your own input/output ratio will move anyway. Pick on capability, context, or latency instead — the monthly bill will look much the same either way. GPT-5.6 Terra is priced at $2.00/M input tokens and $12.00/M output tokens. Gemini 3.1 Pro costs $2.00/M input and $12.00/M output.

On iOPTERA's editorial scores, GPT-5.6 Terra leads with 93/100 for coding and 94/100 for reasoning, against Gemini 3.1 Pro's 88/100 and 89/100.

Capability breakdown

Across the five core benchmark categories, here is how GPT-5.6 Terra and Gemini 3.1 Pro stack up head to head:

coding

GPT-5.6 Terra leads

reasoning

GPT-5.6 Terra leads

data extraction

GPT-5.6 Terra leads

creative tasks

GPT-5.6 Terra leads

vision/multimodal

Gemini 3.1 leads

Best model by task

coding: GPT-5.6 Terra wins with 93/100
reasoning: GPT-5.6 Terra wins with 94/100
data extraction: GPT-5.6 Terra wins with 93/100
creative tasks: GPT-5.6 Terra wins with 92/100
vision/multimodal: Gemini 3.1 Pro wins with 95/100

Estimated monthly cost at scale

For 10M + 2M tokens of text a month (counted the way OpenAI's tokenizer counts), GPT-5.6 Terra runs about $44.00 while Gemini 3.1 Pro runs about $42.68 — Gemini 3.1 Pro saves roughly $1.32 (3%) every month.

What actually decides it

GPT-5.6 Terra and Gemini 3.1 Pro come from different labs, which means different tokenizers, different API shapes, and a second vendor relationship. The same English text does not produce the same token count on both, so a price-per-million comparison understates the difference — measure your own prompts on each before treating the headline rates as the full story.

GPT-5.6 Terra and Gemini 3.1 Pro were released within 5 months of each other, so they are competing on the same evaluations under roughly the same conditions. That makes a direct benchmark comparison meaningful here in a way it usually is not — neither model has the advantage of being measured on a newer, easier set of tests.

Context is effectively a tie: 1.1M against 1.0M. Neither model unlocks a document size the other cannot handle, so this axis should not enter the decision. If you were hoping context would break the tie for you, it will not.

Throughput is close enough to ignore — 86/100 versus 82/100. Neither model will feel noticeably quicker in an interactive product, so latency is not a reason to choose between them.

With prices this close (3% apart), pick on fit rather than cost. GPT-5.6 Terra holds the benchmark edge; weigh that against where each one is weakest — creative tasks and coding respectively — and use the calculator above with your own token mix.

What you actually pay

The list price is only the start. Prompt caching, batch processing and long prompts change the bill, and each provider sets them differently. Prices per 1M tokens.

Pricing terms beyond the list price, per 1M tokens
Pricing term	GPT-5.6 Terra	Gemini 3.1 Pro
List price (input / output)	$2.00 / $12.00	$2.00 / $12.00
Cached input	$0.2010% of the input price	$0.2010% of the input price
Batch API	50% off input and output	50% off input and output
Long prompts	Over 272K tokens: $4.00 / $18.00	Over 200K tokens: $4.00 / $18.00
Input with 80% cache hits	$0.56	$0.56

The last row assumes 80% of input tokens are read from the cache, as in a chat app that re-sends a long system prompt or RAG over the same documents. Cache-write and storage charges are not included.

Gemini also bills cache storage by the hour.

Checked on October 8, 2026 against the pricing pages of OpenAI, Google.

Capability scores

iOPTERA editorial scores across 5 categories — informed by public benchmarks, not measured by us

CategoryGPT-5.6 TerraGemini 3.1Winner

Coding

Reasoning

Extraction

Creative

Vision

GPT-5.6 Terra: 4 wins

Gemini 3.1 Pro: 1 wins

GPT-5.6 Terra leads overall

Speed Score

86/100vs82/100

GPT-5.6Gemini

Context Window

1050Kvs1049K

GPT-5.6Gemini

What Is a Token?

Models don't read words — they process tokens.

A token is roughly 4 characters of English text (~¾ of a word). Your API bill is priced per million tokens — understanding this directly reduces your costs.

Short phrase

"Hello, world!"

4 tokens

GPT-5.6 Terra: $0.80
Gemini 3.1 Pro: $0.78

Business email

One typical email (~200 words)

~270 tokens

GPT-5.6 Terra: $54.00
Gemini 3.1 Pro: $52.38

Code file

50-line Python script

~400 tokens

GPT-5.6 Terra: $80.00
Gemini 3.1 Pro: $77.60

Prices shown are for 100,000 runs of each workload — one run costs a fraction of a cent on both GPT-5.6 Terra and Gemini 3.1 Pro, so the number only becomes meaningful at production volume. Input tokens only; add your output volume in the calculator below.

How to check your token usage

response.usage.total_tokens

Every API response includes a usage object. Sum total_tokens across all calls to get your monthly figure, then use the calculator below.

Your Cost Calculator

Enter your actual monthly token usage to see real savings

Quick Presets

Monthly Token Volume

30M tokens

Prompt / Completion Split

Prompt 70%Completion 30%

GPT-5.6 Terra

$150.00/mo

$1,800.00/yr

$2.00/M input$12.00/M output

Cheaper

Gemini 3.1 Pro

$145.50/mo

$1,746.00/yr

$2.00/M input$12.00/M output

Annual Savings

$54.00 saved per year

Gemini 3.1 Pro cheaper · $4.50/mo

Related Comparisons

Explore similar model pairs to find your best fit

GPT-5.6 TerravsClaude Opus

$2.00 · $5.00/M input

GPT-5.6 TerravsGPT-5.6 Sol

$2.00 · $4.00/M input

GPT-5.6 TerravsClaude Sonnet

$2.00 · $2.00/M input

GPT-5.6 TerravsGrok 4.5

$2.00 · $2.00/M input

GPT-5.6 TerravsGPT-5.2

$2.00 · $1.75/M input

GPT-5.6 TerravsGPT-4o

$2.00 · $2.50/M input

Gemini 3.1vsClaude Opus

$2.00 · $5.00/M input

Gemini 3.1vsGPT-5.6 Sol

$2.00 · $4.00/M input